1. Field of the Invention
The invention relates to a camera shutter provided with a shutter blade for opening and closing a shutter opening provided on a base plate.
2. Description of the Related Art
A conventional camera shutter such as described in, e.g., JP-A 2001-281724 is known (see FIG. 8). An electromagnetic drive shutter described in JP-A 2001-281724 has a driving means for operating a shutter blade but two coils corresponding to two permanent magnets mounted on a driving lever are required in order to drive the driving lever.
In other words, the driving lever starts an operation to open the shutter when an operating current is conducted to two magnetic drive coils at a closing position of the shutter blade, and sequentially, the driving lever starts an operation to close the shutter when the operating current in a reverse direction is conducted to the two magnetic drive coils at an opening position.
In addition, a shutter in a form to operate a shutter blade by rotating a permanent magnet rotor arranged inside a coil by conduction of electricity to one coil is known as a second method.
However, the above-mentioned conventional art requires two coils corresponding to two permanent magnets, and further, a control circuit for conducting electricity to the coils and a component composing a connecting portion to the coils are complicated. In addition, since this coil is a so-called air-cored coil, magnetic flux leakage caused by the conduction of electricity to the coil is likely to occur, compared with the case of having an iron coil. Therefore, energy of the electricity conduction is not effectively used for a shutter operation and the loss thereof is relatively large.
In addition, since obtained power is transmitted by rotating a small rotor arranged inside a coil, the above-mentioned second method has a problem that the obtained power is small and large energy is lost in a transfer pathway.